Workflow Example Horn Antenna

Transcription

1 Workflow Example Horn Antenna Purpose : Optimize the aperture of the horn antenna such that the gain is maximized at 10 GHz. 1 CST MWS - Standard Workflow Choose a project template. Create your model. parameters + geometry + materials Define ports. Set the frequency range. Specify boundary and symmetry conditions. Define monitors. Check the mesh. Run the simulation. 2 1

2 Cylindrical Horn Antenna 8 12 GHz dia=2, rad=1 zlength= units: inch waveguide: 1.0 in x 0.5 in x 0.5 in aperture radius: 1.0 in, length: 0.25 in shell thickness: 0.01 in (outside) monitors: E-field, H-field & far field at 10 GHz 3 Project Template At the beginning choose File -> New to create a new project. For an existing project you may choose File -> Select Template. 4 The project templates customize the default settings for particular types of applications. 2

3 Project Template background material Antennas should be modeled with vacuum as background material. PEC is very practical for closed structures. (e.g. waveguides, connectors, filters) The project templates customize the default settings for particular types of applications. 5 Change the Units Define units. 6 3

4 Horn Antenna Construction (I) Define a brick (1.0 x 0.5 x 0.5 in) made of PEC. Pick face. Align the WCS with the face. 7 Define a cylinder (outer radius: 1.0 in, height: 0.25 in) made of PEC. Move the WCS by 2.0 inches. Horn Antenna Construction (II) Pick two opposite faces. Perform a loft. 8 4

5 Horn Antenna Construction (III) Perform a Boolean add. Select multiple objects (ctrl or shift + left mouse button). shell solid: 0.01 in (outside) Pick two faces. 9 Port Definition Pick point inside corner. Define a waveguide port. Pick edge. 10 Define the port on the internal profile. 5

6 Set the Frequency Range Set the frequency range. 11 Boundary Conditions and Symmetry Planes 12 6

7 3D Monitors Add field monitors for E-field, H-field, and far field at 10 GHz. 13 Mesh View (I) mesh properties 14 7

8 Mesh View (II) TST at work! 15 Transient Solver: Start Simulation The accuracy defines the steadystate monitor. The simulation is finished when the electromagnetic energy in the computational domain falls below this level. 16 8

9 Analyze 1D Results port signals S-parameter energy 17 Analyze 2D/3D Results 18 port information: cut-off frequency line impedance propagation constant 9

10 Electric Field at 10 GHz 19 Far Field at 10 GHz 20 10

11 Polar Plot for Far Field at 10 GHz phi=90 phi=0 21 Create a new folder Comparison to compare different 1D results. Parameterization Optimization 22 11

12 Parameterization (I) r1 outer radius r1 = variable goal: maximize gain 23 Parameterization (II) outer radius r

13 Result Processing Templates (Shift+P) 1D results Define gain(theta) at phi=0. 25 Postprocessing templates provide a convenient way to calculate derived quantities from simulation results. Each template is evaluated for each solver run. Result Processing Templates (Shift+P) 0D results Define max of gain(theta). Read the online help to learn more about the postprocessing in CST MWS

14 Result Processing Templates (Shift+P) Alternative solution: The maximum gain can be computed using the Farfield template in 0D Results. Define max of gain(theta). 27 Parameter Sweep - Settings

15 Parameter Sweep - Settings Add a S-parameter watch. The results will be automatically listed in the Tables folder. 29 Parameter Sweep Table Results Right click on plot window and select Table Properties. Choose the result curve for each parameter value with the slider

16 Parameter Sweep Table Results parameter values parameter values 31 Automatic Optimization 32 16

17 Automatic Optimization Define the parameter space. Define the goal function. Template based postprocessing 0D results can be used to define very complex goal functions. 33 Automatic Optimization Choose the Classic Powell optimizer. Follow the optimization

18 Automatic Optimization - Results parameter values 1D results goal: maximize gain 35 Optimization - Summary Define a variable. Parameterize the structure. Define the goal function. Set the parameter space. Run the optimizer

19 Far Field Postprocessing terminology broadband far field analysis co-/cross-polarization phase center tips and tricks 37 Broadband Far Field Analysis How to plot the antenna gain for the complete frequency range? 38 19

20 Broadband Far Field Monitors Create a broadband far field monitor from the available monitors. After monitor definition, start T-solver again! 39 Result Processing Templates (Shift+P) 1D Results Define maximum value of gain

21 Broadband Far Field Monitors far field 3D pattern 41 Broadband Far Field Monitors 42 21

22 Tables -> 1D Results -> Broadband gain 3d 43 Co- / Cross-Polarization The co-polarized far field component has the same polarization as the excitation (y-oriented in our case). The cross-polarized far field component is orthogonal to the co-polarized component and main lobe direction. 44 In order to use different polarizations for transmitting/receiving, an antenna design goal might be to maximize the co-polarized and minimize the cross-polarized component. 22

23 Co- / Cross-Polarization 1. Select the tab Axes. 2. Click Main lobe/polarization alignment. 3. Choose the Ludwig 3 coordinate system. polarization vector direction (arbitrary user input possible). 45 If Main lobe... is not selected, the user can enter arbitrary directions for: -polarization plane normal (z ) (= theta axis) -cross-polarized component (x ) (= phi axis). Co- / Cross-Polarization co-polarized = Ludwig 3 vertical cross-polarized = Ludwig 3 horizontal 46 23

24 Co & Cross Polarization Result Templates for Parameter Sweep and Optimization co-polarized= Ludwig 3 vertical cross-pol. = Ludwig 3 horizontal 47 Phase Center Calculation Finding the best location to place the horn inside a parabolic antenna. The best position is to match the focal point of the dish with the phase center of the horn. = y z plane = x z plane? 48 24

25 Check Phase Center Check the phase center by plotting the Ludwig 3 vertical phase. Plotting the phase of Ludwig 3 vertical (=dominant component of co-polarized fields) does not result in a 180 jump of the phase (=color jump) at theta=0. 49 Check Phase Center Check the phase center by moving the origin to the phase center. 50 See also article (Phase Center comparison with measurements) on -> application article ID=256 25